Salt tectonics and tear faulting in the central part of the Zagros Fold-Thrust Belt, Iran

Jahani, Salman; Hassanpour, Jafar; Mohammadi-Firouz, Samaneh; Letouzey, J.; Lamotte, Dominique Frizon de; Alavi, Seyed Ahmad Naseri; Soleimany, Bahman

doi:10.1016/j.marpetgeo.2017.06.003

Cited by 56 publications

(37 citation statements)

References 84 publications

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“…Three different evaporitic units had a significant contribution to development of the Neogene folding in the Zagros fold-and-thrust belt; the Oligocene Fars salt in the southern Persian Gulf (Jahani et al, 2009), the infra-Cambrian Hormuz salt in the Fars arc (Callot et al, 2012;Jahani et al, 2017), and the lower Miocene Gachsaran salt in the north Dezful Embayment (this study) ( Figure 13). Seismic lines and fieldwork indicate that both the Fars and Gachsaran salts initially formed salt walls even before peak folding in their respective areas.…”

Section: Implications Of the Interaction Between Compression And DImentioning

confidence: 68%

“…A large number of both exposed and buried Cambrian salt diapirs, known as the Hormuz diapirs, characterize the Fars arc and the Persian Gulf domains, except on the Qatar‐Fars palaeo‐high (e.g. Jahani et al., ; Kent, ; Talbot & Alavi, ), (Figure b). The absence of salt diapirs to the west of the Kazerun Fault zone is interpreted to be due to the lack of the Cambrian Hormuz salt at the base of sedimentary cover in the Dezful and Lurestan domains (e.g.…”

Section: Introduction and Geological Settingmentioning

confidence: 99%

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Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

et al. 2018

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Differentiating compressional growth strata from halokinetic sequences is not straightforward in foreland fold‐and‐thrust belts where compressional and diapiric processes were coeval. Although there are numerous studies on the role of salt layers in fold‐and‐thrust belts, very few focus on syntectonic evaporites where they are thick enough to develop diapirism. The tectonic structures of the northern Dezful Embayment, along the footwall of the Zagros Mountain Front Fault, show a complex evolution interpreted in this study by the concurrence of folding, thrusting and pre‐ and syn‐shortening diapirism of the lower Miocene Gachsaran evaporites. We explore this tectonic–diapiric–sedimentary interplay by combining field studies and remote‐sensing mapping, detailed stratigraphy and sedimentology, high‐quality seismic data, and step‐by‐step balanced tectono‐sedimentary restorations. Initial diapirism occurred soon after the deposition of at least 1.5 km thick Miocene Gachsaran evaporites during the sedimentation of up to 5 km thick Aghajari, Lahbari and Bakhtyari formations, which display syntectonic mixed growth strata and halokinetic sequences. These sedimentary sequences filled salt‐related minibasins, from which the Azanak Minibasin is the deepest, limited by growing salt walls and salt anticlines (Azanak thrust‐weld and the Saland–Lali anticline). Palaeocurrents and clasts compositions document fluvial diversions and exposure and erosion of Gachsaran evaporites along the active salt walls. Although, by further shortening, the precursor salt walls squeezed and reactivated as thrust‐welds structuring a duplex of overriding minibasins. During the deposition of the middle‐late Miocene Aghajari Formation, Kazhdumi and Pabdeh source rocks were buried to oil‐expulsion depths, and Sarvak and Asmari reservoirs were mildly folded in large and open anticlines. The Gachsaran system in the northern Dezful Embayment is collated with the structures of preshortening Hormuz salt and syn‐shortening Fars salt to highlight the important role of these ductile units in the tectonic evolution of the Zagros fold belt that is compared to syn‐compressional salt‐related Pyrenees, Carpathians, Sivas and Kuga fold belts.

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Section: Implications Of the Interaction Between Compression And DImentioning

confidence: 68%

Section: Introduction and Geological Settingmentioning

confidence: 99%

Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

et al. 2018

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“…The Zagros hosts the most productive reservoir rocks in the world, prompting interest in its subsurface structure and stratigraphy. According to offshore seismic reflection profiles in the central and eastern Persian Gulf, the total (undeformed, unexumed) cover thickness is ∼12-16 km (Jahani et al, 2009;Jahani et al, 2017), while balanced cross sections in the foreland of the northwestern Zagros show cover thicknesses there of ∼11-14 km (e.g., Blanc et al, 2003;Casciello et al, 2009;. These values are somewhat greater than cover thicknesses from balanced cross sections across the SFB itself, which range from ∼6-10 km in the Lurestan arc (e.g., Blanc et al, 2003;Farzipour-Saein et al, 2009;Homke et al, 2009;McQuarrie, 2004; to ∼9-15 km in the Dezful embayment and Fars arc (e.g., Ahmadhadi et al, 2007;Blanc et al, 2003;Derikvand et al, 2018;Sherkati et al, 2006).…”

Section: Stratigraphy Geology and Structurementioning

confidence: 99%

Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

et al. 2019

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We use calibrated earthquake relocations to reassess the distribution and kinematics of faulting in the Zagros range, southwestern Iran. This is among the most seismically active fold‐and‐thrust belts globally, but knowledge of its active faulting is hampered by large errors in reported epicenters and controversy over earthquake depths. Mapped coseismic surface faulting is extremely rare, with most seismicity occurring on blind reverse faults buried beneath or within a thick, folded sedimentary cover. Therefore, the distribution of earthquakes provides vital information about the location of active faulting at depth. Using an advanced multievent relocation technique, we relocate ∼2,500 earthquakes across the Zagros mountains spanning the ∼70‐year instrumental record. Relocated events have epicentral uncertainties of 2–5 km; for ∼1,100 of them we also constrain origin time and focal depth, often to better than 5 km. Much of the apparently diffuse catalog seismicity now collapses into discrete trends highlighting major active faults. This reveals several zones of unmapped faulting, including possible conjugate left‐lateral faults in the central Zagros. It also confirms the activity of faults mapped previously on the basis of geomorphology, including oblique (dextral‐normal) faulting in the NW Zagros. We observe a primary difference between the Lurestan arc, where seismicity is focused close to the topographic range front, and the Fars arc, where out‐of‐sequence thrusting is evident over a width of ∼100–200 km. We establish a focal depth range of 4–25 km, confirming earlier suggestions that earthquakes are restricted to the upper crust but nucleate both within and beneath the sedimentary cover.

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“…The interpretation of seismic profiles from the Central Persian Gulf indicates that the Hormuz Salt began moving at the Early Palaeozoic (Jahani et al, 2009(Jahani et al, , 2017Perotti et al, 2016), but the precise age of the oldest synkinematic strata remains unknown because they are undrilled. In Oman, the Ara Salt movement initiated during deposition of the Lower Cambrian Nimr Group sediments (e.g.…”

Section: Salt Basins and Halokinesismentioning

confidence: 99%

Salt tectonics in a double salt‐source layer setting (Eastern Persian Gulf, Iran): Insights from interpretation of seismic profiles and sequential cross‐section restoration

et al. 2020

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Salt tectonics in the Eastern Persian Gulf (Iran) is linked to a unique salt‐bearing system involving two overlapping ‘autochthonous’ mobile source layers, the Ediacaran–Early Cambrian Hormuz Salt and the Late Oligocene–Early Miocene Fars Salt. Interpretations of reflection seismic profiles and sequential cross‐section restorations are presented to decipher the evolution of salt structures from the two source layers and their kinematic interaction on the style of salt flow. Seismic interpretations illustrate that the Hormuz and Fars salts started flowing in the Early Palaeozoic (likely Cambrian) and Early Miocene, respectively, shortly after their deposition. Differential sedimentary loading (downbuilding) and subsalt basement faults initiated and localized the flow of the Hormuz Salt and the related salt structures. The resultant diapirs grew by passive diapirism until Late Cretaceous, whereas the pillows became inactive during the Mesozoic after a progressive decline of growth in the Late Palaeozoic. The diapirs and pillows were then subjected to a Palaeocene–Eocene contractional deformation event, which squeezed the diapirs. The consequence was significant salt extrusion, leading to the development of allochthonous salt sheets and wings. Subsequent rise of the Hormuz Salt occurred in wider salt stocks and secondary salt walls by coeval passive diapirism and tectonic shortening since Late Oligocene. Evacuation and diapirism of the Fars Salt was driven mainly by differential sedimentary loading in annular and elongate minibasins overlying the salt and locally by downslope gliding around pre‐existing stocks of the Hormuz Salt. At earlier stages, the Fars Salt flowed not only towards the pre‐existing Hormuz stocks but also away from them to initiate ring‐like salt walls and anticlines around some of the stocks. Subsequently, once primary welds developed around these stocks, the Fars Salt flowed outwards to source the peripheral salt walls. Our results reveal that evolving pre‐existing salt structures from an older source layer have triggered the flow of a younger salt layer and controlled the resulting salt structures. This interaction complicates the flow direction of the younger salt layer, the geometry and spatial distribution of its structures, as well as minibasin depocentre migration through time. Even though dealing with a unique case of two ‘autochthonous’ mobile salt layers, this work may also provide constraints on our understanding of the kinematics of salt flow and diapirism in other salt basins having significant ‘allochthonous’ salt that is coevally affected by deformation of the deeper autochthonous salt layer and related structures.

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Salt tectonics and tear faulting in the central part of the Zagros Fold-Thrust Belt, Iran

Cited by 56 publications

References 84 publications

Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

Seismotectonics of the Zagros (Iran) From Orogen‐Wide, Calibrated Earthquake Relocations

Salt tectonics in a double salt‐source layer setting (Eastern Persian Gulf, Iran): Insights from interpretation of seismic profiles and sequential cross‐section restoration

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